Adsorption of vitamin B12 to alumina, kaolinite, sand and sandy soil

Vitamin B12 is an important component of media used to stimulate the growth of many anaerobic microbes that dechlorinate aliphatic compounds. Its delivery to the subsurface is therefore a concern for enhanced in situ bioremediation and bioaugmentation. In situ circulation of vitamin B12 and a chemical reductant has also been field tested for treatment of chlorinated methanes, ethanes, and ethenes. The objective of this study was to determine the extent of B12 (added as cyanocobalamin) adsorption to aquifer solids. Batch studies indicated a minor amount of adsorption to kaolinite clay (Freundlich Kf=1.5 ((mu)g/g) (mL/(mu)g)1/n and 1/n=0.39) and sand (Kf=0.70 ((mu)g/g) (mL/(mu)g)1/n and 1/n=0.84), and no detectable adsorption to alumina. Column studies using a 3H2O tracer and vitamin B12 in distilled water (10 (mu)M) resulted in a B12 retardation factor (R) of approximately 2 for both sand (0.14% organic carbon) and a sandy soil (2.5% organic carbon). Using groundwater containing organic carbon (2.8 mg/L) in place of distilled water did not significantly change R. The relatively low value for R indicates vitamin B12 can be distributed throughout a contaminated aquifer without experiencing significant losses to adsorption.